The Influence Analysis Of Construction Defects To The Dynamic Characteristics Of The Two-equal-span Curved Box Girder Bridges

With the requirements of the modern transportation is increasing day by day, the curved girder bridges occupies a very important position in transportation engineering. Numbers and design requirements of the curved girder bridges are constantly improving. The research results about the curved girder bridge diseases are very rich. But they still stay on static analysis. Construction defect is one of the important factors causing the curved girder bridge diseases. Especially for the construction defects which may cause dynamic characteristic changes to curve box girder bridge, the theory of dynamic analysis is more needed to use in the further research.The construction defects appeared in the curved box girder bridges were studied, three common construction defects which influenced the dynamic performance of the curve box grider bridges were analyzed and summarized. Two-equal-span curved box girder bridge models were established, in which construction defects were simulated by using the finite element analysis software which is widely accepted in the engineering. Construction defects in the curved box girder bridges were studied as a part of bridge diseases in the past, and a large number of data showed that construction defect was one of the main reasons of the bridge diseases, it is important to study construction defects.Dynamic Characteristic parameters of normal models and unnormal models with defects were studied by modal analysis method, whose data were compared. The influence law of construction defects were concluded. The results showed that bridge bearing failure made the most importmant influence on the dynamic characteristics during construction, then was the strength of concrete; the influence of crack, pits, hole defects and others on the dynamic properties are very limited, almost without any influence on the construction of curve box girder bridges.The specific influences are as follows:along with the number of failure bearing increases, model frequency presented the tendency of increase and individual modal frequency amount is larger, and the change of model maximum displacement amplitude presented accelerated trend. When failure bearings took place in different piers, the frequency increased sharply. If the two failure bearings took place in the same piers, frequency increases slowly. When failure bearings take place in different piers, maximum displacement of vibration increases sharply. If the two failure bearings take place in the same piers, maximum displacement of vibration increases slowly. The change of concrete strength affects the modal frequency obviously. Modal frequency increases gradually with the increase of concrete strength. The higher the strength of the concrete is, the higher modal frequency is, showing good correlation between them. The influence of the change of concrete strength on the maximum displacement of vibration is very small. The calculated data discussed in this paper shows almost no influence. The mode of curved box girder bridge changed a little with the opening size of roof. So it could be speculated, the openings on other parts of curved box girder bridges can not influence the mode bridges.